A process is described in U.S. Pat. No. 4,234,632 (Lubowitz) by the present inventor for the fabrication of waste forms by molding with match dye molds. Toxic material is mixed with thermosetting resin and the mixture is charged into an agglomeration mold where it is confined and subjected to heat to form an agglomerate. The free standing agglomerate placed in a second mold is then covered by powdered and/or pelletized thermoplastic resin and consolidated therein by heating and solidified by cooling thereby resin jacketing the agglomerate on the top and sides. The partially encapsulated agglomerate is then inverted in the mold. The untreated bottom of the agglomerate is covered with additional thermoplastic resin that is heated and solidified. During the heating and solidification of the resin, it fuses with that on the rim of the preformed jacket to complete resin encapsulation of the agglomerate.
A commercially viable full scale production apparatus and method for practicing the process of the above described patent for treating hazardous wastes is described in U.S. Pat. No. 4,756,681 (Unger-1), U.S. Pat. No. 4,859,395 (Unger-2), and U.S. Pat. No. 4,932,853 (Unger-3) all by the present inventor, Unger, and Telles. These patents describe a three stage mold and a method for using same. In the first of three stages, a large volume of waste material is admixed with a thermosetting resin and transferred to an agglomeration mold. The moldable admixture of waste material and thermosetting resin is confined therein and transformed into a dimensionally stable agglomerate by the application of heat. The free standing agglomerate is then enveloped in the second stage by a jacketing mold, and submerged by thermoplastic resin, as powder and/or pellets, added in the space between agglomerate and jacketing mold and to the top of the agglomerate. After the application of heat and moderate pressure, a jacket of thermoplastic resin approximately 6 mm. ( 1/4 inch) thick, fused onto the sides and top of the agglomerate, forms upon cooling the mold. In the third stage, the partially, encapsulated agglomerate and mold are inverted together. Additional powder and/or pellets is added and fused onto the former bottom of the agglomerate and to the rim of the preformed jacket to form a fully jacketed agglomerate. Once complete, the waste form exhibits seamless resin encapsulation of the agglomerate. Inversion of agglomerate and mold together, allowed by the equipment and the method, significantly advances large scale management of hazardous wastes. A large volume of hazardous waste is encapsulated by protective thermoplastic resin. The seam free jacket of thermoplastic resin fused upon the surface of the agglomerate gives rise to waste forms that withstand severe stresses of transportation, leaching stresses and physical stresses, such as freeze-thaw and wet-dry, that may occur in a landfill. Additional references with respect to this process are chapters of two books: "Surface Encapsulation Process for Stabilizing Intractable Contaminants", by Unger, Telles and Lubowitz (the present inventor), pp. 40-52, Environmental Aspects of Stabilization and Solidification of Hazardous and Radioactive Wastes,.COPYRGT.1989, ASTM STP 1033, Pierre Cote and Michael Gilliam, editors; and "EPP Process for Stabilization/Solidification of Contaminants" by Unger and Lubowitz (the present inventor), pp. 77-86, Physical/Chemical Processes, Innovative Hazardous Waste Treatment Technology Series,.COPYRGT.1990, Volume 2, Technomic Publishing Co., Inc., edited by Harry M. Freeman.
Other methods of waste management entail surface treatment of agglomerates, such as spraying or dipping of the agglomerate in a suitable coating material such as asphaltum or wrapping in a wire mesh, as disclosed in U.S. Pat. No. 3,330,088. Alternatively, the agglomerated wastes may be wrapped in a vinyl sheet as disclosed in U.S. Pat. No. 3,451,185. The large scale processes described in these two patents may be suitable for the management of general refuse but they are not suitable for achieving high performance management of low energy radioactive wastes and industrial hazardous wastes. The art described by Unger 1, 2 and 3, in contrast, yields processing advantages, and waste forms that secure contaminants under harsh environmental stresses of waste management due to leaching, overburden, alternative wet and dry conditions, alternative freezing and thawing conditions, and mechanical impact.
The use of polyethylene for management of contaminated ion exchange resin particulates and of evaporator concentrates is disclosed by Norboru et al. in Nuclear and Chemical Waste Management.COPYRGT.1982, Vol. 3, pp. 23-28 and 131-137. Norboru discloses that polyethylene is a superior binder for this purpose. But waste forms resulting in the above art hold low concentration of wastes due to the difficulty of effectively blending high concentrations into polyethylene resin.
Other methods of disposing of wastes include confining them in plastic or metal containers, or mixing wastes with binder materials such as aqueous cements and resins, and solidifying mixtures of wastes and binder in the containers. All of these methods have significant disadvantages. Both plastic and metal containers require prefabrication prior to waste management and thus they entail transporting appreciable unoccupied volume, and in addition, have a high relative initial cost. Containers are also subject to such problems as ineffective sealing and corrosion which eventually allows leaching and seepage of the contents. Even the combination of confining waste and binder mixtures in containers does not assure effective waste stabilization due to the shortcomings of containers.
None of the above techniques address the issue of dust and/or leakage of containments during the process of confining or securing toxic materials. Due to the nature of the techniques, workers practicing the above waste management processes need appreciable provisions for protection against contamination by such wastes. Waste materials may escape by dust formation, leakage, fragmentation, etc. Consequently, a need exists for improved techniques for abating the contamination of work places in the management of toxic waste and for fabricating high performance waste forms.